The need to back up data is ubiquitous. As the amount of data to be backed up continues to grow, more and more sophisticated approaches to backup are desired. Grandfather-father-son (GFS) sets of backup images are known to those skilled in the art. In some instances, a GFS set of backup images may have all the data needed to create a synthetic full backup. Thus, a backup application may attempt to specify a new backup image in terms of previous backup images including full backups and incremental backup images. This specification may take the form of instructions like, for example, “take x bytes from backup B1 starting at location L1 and then take y bytes from backup B2 starting at location L2 . . . ” The backup application may be unconcerned with where or how the actual underlying data is stored. For example, the data may be stored on tapes, in solid state devices, on disks, or elsewhere. Regardless of how or where it is stored, the new backup image can be specified in terms of the old backup image(s).
A synthetic backup is created by collecting data from a previous backup(s) rather than from an original source. The backup is referred to as a “synthetic” backup because it is not a backup created from original data. A synthetic full backup does not actually transfer data from an original non-backed up source (e.g., client computer) to backup media. Instead, to the extent a synthetic full backup transfers data, it may transfer data from one backup media to another backup media.